Issue Summary

Bamboo v12.1.9 does not create a PR plan branch when the "When a pull request is created" automatic branch management trigger is configured, if a regular branch plan already exists for the PR's source branch.

Steps to Reproduce

1. Set up Bamboo with a linked Bitbucket repository via Application Links
2. Configure a plan's Automatic Branch Management to "When new branch in repository is created"
3. Create a new branch (e.g., branch3) in Bitbucket. Confirm Bamboo creates a branch plan
4. Change the plan's Automatic Branch Management trigger to "When a pull request is created"
5. Create a new PR in Bitbucket from branch3 → master
6. Observe that Bamboo does not create a PR plan branch

Expected Results

Bamboo should create a separate PR-linked plan branch (with a numbered suffix) even when a regular branch plan already exists. This works correctly on Bamboo 10.2 but is broken on 12.1.9.

Actual Results

Bamboo silently ignores the incoming PR remote event and does not create a PR plan branch.

Workaround

Currently there is no known workaround for this behavior. A workaround will be added here when available